An update on the use of genetic manipulation (GM) and gene editing (GE) in sugarcane was the subject of an ASSCT paper co-authored by SRA Research Mission Managers Dr Stephen Mudge and Dr Muyiwa Olayemi.
Genetic Manipulation or Genetic Modification (GM) uses lab-based technologies to add foreign DNA to the genes of organisms. Gene Editing is inserting a mutation into specifically targeted genes of the organism using Site Directed Nucleases (SDN) cutting technologies – SDN-1,-2 and -3. Using SDN-1 the mutation is introduced without incorporating any foreign DNA into the genome. The advantage is that the result is not considered to be a Genetically Modified Organism (GMO) so it doesn’t need government approval to be released.
“Why should the sugarcane industry look at GM again?” Dr Mudge asked. “Firstly, there have been many technological improvements in the past few years, particularly with Gene Editing. Secondly, the industry is under increasing pressure to reduce agricultural chemical use. Growers may lose access to key chemicals. We need to look for non-chemical alternatives for controlling pests and diseases. Thirdly, Brazil has already commercialised both GM and GE sugarcane lines in their industry with favourable effects.”
In Stephen’s role as SRA’s Research Mission Manager for the Crop Protection Program, he has worked with Plant Health Australia to update the Industry Biosecurity Plan which is due for release soon.
“The new plan has rated seven species of exotic moth borer as Extreme Risk to the industry, capable of causing up to 20 percent yield loss on their own, or total loss where multiple species are involved. In 2017, Brazil released their first insect-resistant GM sugarcane using Bt technology.”
Bt is a family of insecticidal proteins from the bacterium, Bacillus thuringiensis. Brazil aims to have 20 percent of the industry growing GM sugarcane by 2030.
“Trials have shown that in most cases, there’s no borer damage to Bt sugarcane in Brazil,” Dr Mudge said.
In terms of GM crops elsewhere, the United States leads the way with more than 90 percent GM soybean, cotton and corn crops, mostly Bt. Almost 100 percent of American sugar beet crops are herbicide tolerant. This accounts for about half the domestic sugar produced and consumed in the United States. In Australia, more than 99 percent of the cotton crop is GM because of a crisis caused by the cotton bollworm, Helicoverpa. The first GM Bt cotton, was released in 1996.
“According to a cotton grower involved in the first trials, his farm went from 19 sprays per season down to none following the adoption of GM. However, all growers must follow a very strict farm management plan to prevent insect resistance developing in the industry. Bt cotton and the management process are expensive.”
Stephen spoke about his own experience working with GM sugarcane for about 10 years at the University of Queensland.
“The project produced a high value sugar in sugarcane called isomaltulose which does not cause tooth decay and has a low GI. In addition, for a period of about six years BSES partnered with DuPont to develop and field test herbicide tolerant cane. In terms of feasibility, we have already demonstrated that we can generate and field test hundreds, even thousands, of independent GM sugarcane lines.”
Stephen said the biggest opportunity for GM sugarcane in the industry today was insect control.
“The Bt technology is tried and tested, particularly for lepidoptera such as exotic moth borers. Other opportunities include incorporating Bt toxins that are effective against the larvae of Coleoptera (an order of insects which includes cane grubs) and Diptera (which includes soldier flies). Another opportunity is in ribonucleic acid (RNA) interference – RNAi. An RNAi project has been funded by SRA for the past few years.
“The active ingredient for RNAi is double stranded RNA. The project is investigating ways to apply stabilised double-stranded RNA to the surface of the plant so that it gets absorbed. Its biggest advantage is that it can be highly species specific so that off target effects are much less of an issue. However, using GM, every cell of the plant could produce large amounts of the double-stranded DNA, resulting in much better efficacy.”
Dr Mudge said that negative public perception is still a barrier to GM technology. In addition, ensuing continued trade and market access is critical in any decision made about introducing these technologies.
